Westbound traffic on the H-1 freeway was still slow-moving Tuesday night, some eight hours after an oil spill snarled traffic.

Police said the oil spill occurred about 11 a.m. in a construction area on the H-1 near the Waimalu offramp, backing up westbound traffic.

The HOV lane was opened to all vehicles following the oil spill. The state Department of Transportation opened the HOV lane to all vehicles at about 5:14 p.m. 

Cones blocking off the construction area were supposed to be removed at 2 p.m., but that was delayed because the spill wasn’t completely removed, which contributed to the gridlock, police said.